Before an application was prepared, a preliminary search was conducted in the United States Patent Office. The search covered United States patents officially classified and cross-referenced in, and publications and foreign patents collected by the examiners in: Class 273 Games, subclasses 130, 131, 135, 136, 137, 156 and 157; Class 35 Teaching, subclass 27; and in Class 46 Amusement Devices, subclasses 16, 25 and 28. The fields of search were discussed with Patent Office Examiner Lowe. Examples of the most pertinent U.S. Pat. Nos. which were found are: 3,302,310, 3,403,460, 3,672,681, 3,674,274, 3,788,645, 2,819,904, 2,570,625.
U.S. Pat. No. 3,302,310 describes sides with interfitting features.
U.S. Pat. No. 3,403,460 shows four variable sides of blocks. FIG. 14.
U.S. Pat. No. 3,672,681 shows all sides of blocks are identical.
U.S. Pat. No. 3,674,274 has colored sides with colored dots on sides.
U.S. Pat. No. 3,788,645 describes a colored cube puzzle, but no interfitting or repellent feature is disclosed.
U.S. Pat. Nos. 2,819,904 and 2,570,625 were selected for their showings of magnets in blocks.